Core Java

Java: Mocking a ResultSet using Mockito

This post shows how you can mock a java.sql.ResultSet using Mockito. It can be used to help unit test code which performs operations on ResultSets (such as a ResultSetExtractor) without relying on an external datasource.

You can create a MockResultSet by providing a list of column names and a 2D array of data. For example:

var rs = MockResultSet.create(
           new String[] { "name", "age" }, //columns
           new Object[][] { // data
             { "Alice", 20 },
             { "Bob", 35 },
             { "Charles", 50 }

The code for MockResultSet is shown below (also available in my GitHub Repository). Note that I have only mocked a few methods such as next, getString and getObject but it is quite easy to mock the rest by following the same pattern.

public class MockResultSet {

  private final Map<String, Integer> columnIndices;
  private final Object[][] data;
  private int rowIndex;

  private MockResultSet(final String[] columnNames,
                        final Object[][] data) {
    // create a map of column name to column index
    this.columnIndices = IntStream.range(0, columnNames.length)
            k -> columnNames[k],
            (a, b) ->
              { throw new RuntimeException("Duplicate column " + a); },
            )); = data;
    this.rowIndex = -1;

  private ResultSet buildMock() throws SQLException {
    final var rs = mock(ResultSet.class);

    // mock
    doAnswer(invocation -> {
      return rowIndex < data.length;

    // mock rs.getString(columnName)
    doAnswer(invocation -> {
      final var columnName = invocation.getArgumentAt(0, String.class);
      final var columnIndex = columnIndices.get(columnName);
      return (String) data[rowIndex][columnIndex];

    // mock rs.getObject(columnIndex)
    doAnswer(invocation -> {
      final var index = invocation.getArgumentAt(0, Integer.class);
      return data[rowIndex][index - 1];

    final var rsmd = mock(ResultSetMetaData.class);

    // mock rsmd.getColumnCount()

    // mock rs.getMetaData()

    return rs;

   * Creates the mock ResultSet.
   * @param columnNames the names of the columns
   * @param data
   * @return a mocked ResultSet
   * @throws SQLException
  public static ResultSet create(
                         final String[] columnNames,
                         final Object[][] data)
                         throws SQLException {
    return new MockResultSet(columnNames, data).buildMock();
Published on Java Code Geeks with permission by Fahd Shariff, partner at our JCG program. See the original article here: Java: Mocking a ResultSet using Mockito

Opinions expressed by Java Code Geeks contributors are their own.

Fahd Shariff

Fahd is a software engineer working in the financial services industry. He is passionate about technology and specializes in Java application development in distributed environments.
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Newest Most Voted
Inline Feedbacks
View all comments
Oscar Mejía
Oscar Mejía
3 years ago

Hey Thanks a lot!

2 years ago

bhai how to use it in our project

11 months ago

I think that this implementation missed that ResultSet implementations should follow the contract that column indexes start from 1 and not 0, see:

Back to top button